U.S. patent number 7,073,405 [Application Number 10/324,073] was granted by the patent office on 2006-07-11 for sensor for profiling system.
This patent grant is currently assigned to Global E Bang Inc.. Invention is credited to Daniel Rioux.
United States Patent |
7,073,405 |
Rioux |
July 11, 2006 |
Sensor for profiling system
Abstract
A sensor for detecting an acceleration on a surface. The sensor
exchanging messages with a computer through a communication
interface. The sensor comprises an accelerometer for outputting a
signal representative of the acceleration and an interface unit
comprising a transmitting circuit. The interface unit receives the
signal representative of the acceleration and modulates the signal
for transmission to the computer.
Inventors: |
Rioux; Daniel (Laval,
CA) |
Assignee: |
Global E Bang Inc. (Quebec,
CA)
|
Family
ID: |
4170947 |
Appl.
No.: |
10/324,073 |
Filed: |
December 20, 2002 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20030174579 A1 |
Sep 18, 2003 |
|
Foreign Application Priority Data
|
|
|
|
|
Dec 20, 2001 [CA] |
|
|
2366030 |
|
Current U.S.
Class: |
73/866.5;
73/493 |
Current CPC
Class: |
G01V
1/16 (20130101); G01V 1/22 (20130101) |
Current International
Class: |
G01D
21/00 (20060101); G01P 1/02 (20060101) |
Field of
Search: |
;73/493,866.5,514.33,514.16,431,514.32,514.34 ;324/162,166 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0 340 476 |
|
Nov 1989 |
|
EP |
|
WO 84/01026 |
|
Mar 1984 |
|
WO |
|
Primary Examiner: Kwok; Helen
Claims
The invention claimed is:
1. A sensor for detecting an acceleration on a surface, said sensor
exchanging messages with a computer through a communication
interface, said sensor comprising: a. an accelerometer for
outputting a signal representative of said acceleration; and b. an
interface unit comprising a transmitting circuit, said interface
unit receiving said signal representative of said acceleration and
modulating the signal for transmission to said computer, wherein
said interface unit further comprises an automatic gain amplifier
for amplifying said signal; c. a processor connected to said
accelerometer and said interface unit for controlling and managing
said accelerometer and said interface unit; and d. a positioning
circuit connected to said processor.
2. The sensor of claim 1, wherein said accelerometer comprises a
semi conductor substrate.
3. The sensor of claim 2, wherein said semi conductor substrate
comprises at least one of a Strain gauge, a capacitor, and a
piezo-electrical device.
4. The sensor of claim 1, wherein said signal representative of
said acceleration comprises an analog electrical signal and wherein
said interface unit further comprises an analog-to-digital
converter for converting said analog electrical signal to a digital
signal.
5. The sensor of claim 4, wherein said interface unit further
comprises a control circuit for controlling at least one of a level
of amplification of said automatic gain amplifier and a dynamic
range of said analog-to-digital converter.
6. The sensor of claim 4, wherein said interface unit further
comprises an a frequency filtering means for filtering said analog
electrical signal.
7. The sensor of claim 3, further comprising a power source
providing electrical power to said substrate and said interface
unit.
8. The sensor of claim 7, wherein power to said substrate and said
interface unit is provided external said sensor.
9. The sensor of claim 2, wherein said semi conductor substrate
comprises at least one of a strain gauge etched directly onto, a
strain gauge build up by deposit onto, and a strain gauge glued
onto said semi conductor substrate.
10. The sensor of claim 2, wherein said semi conductor substrate
comprises two strain gauge assemblies and two matched resistors
forming a Wheatstone bridge, said two strain gauge assemblies
located on two opposite branches of said Wheatstone bridge, and
said two matched resistors located on the other two opposite
branches of said Wheatstone bridge.
11. The sensor of claim 10, wherein each of said two strain gauge
assemblies comprises two strain gauges connected in parallel.
12. The sensor of claim 11, wherein said substrate comprises a
calibration resistor placed in parallel with one of said two
matched resistors.
13. The sensor of claim 1, wherein said transmitting circuit
comprises at least one of an antenna and an optical transceiver
relaying at least one of said signal and messages through said
communication interface.
14. The sensor of claim 13, further comprises a memory means
connected to said processor for storing at least one of samplings
of said signal representative of said acceleration and instructions
for operation of said processor.
15. The sensor of claim 14, wherein said positioning circuit
comprises at least one of a gyroscope and a Global Positioning
System.
16. A sensing assembly comprising at least two sensors of claim
15.
17. The sensing assembly of claim 16, wherein said at least two
sensors are In communication with each other.
18. The sensing assembly of claim 17, wherein said memory means
stores a unique identifier for each one of said at least two
sensors.
19. A sensor for detecting an acceleration on a surface, said
sensor exchanging messages with a computer through a communication
interface, said sensor comprising: a. a substrate comprising an
accelerometer for outputting a signal representative of said
acceleration; b. a mass attached to said substrate, said mass
moving in response to said acceleration, wherein said substrate
comprises an opening within which said mass is supported; and c. an
Interface unit comprising a transmitting circuit, said Interface
unit receiving said signal representative of said acceleration and
modulating the signal for transmission to said computer.
20. The sensor of claim 19, wherein said accelerometer comprises a
semi-conductor substrate.
21. The sensor of claim 20, further comprising: a. a housing
supporting said semi conductor substrate; and b. a damping element
mounted between said housing and said mass.
22. The sensor of claim 21, wherein said damping element comprises
material being resistant to fatigue.
23. The sensor of claim 22, wherein said material resistant to
fatigue comprises at least one of neoprene and silicone.
24. The sensor of claim 23, further comprising a shock absorbing
element between said damping element and said housing.
25. The sensor of claim 21, wherein said housing comprises a bottom
plate which provides a physical interface between said sensor and
said surface.
26. The sensor of claim 25, wherein said housing further comprising
a casing mounted on said bottom plate.
27. The sensor of claim 26, wherein said housing further comprising
a top cover hermetically mounted on said casing.
28. The sensor of claim 25, wherein said bottom plate comprises
attachment means for providing attachment of said sensor to said
surface.
29. The sensor of claim 28, wherein said attachment means comprises
at least one of a threaded attachment, an adhesive, a weight, a
magnetic material device, and an explosive driven type anchor.
30. The sensor of claim 29, wherein said housing comprises an
electrically conductive surface for substantially shielding said
sensor from electromagnetic interference.
31. The sensor of claim 30, wherein said transmitting circuit
comprises at least one of an antenna and an IR diffuser relaying at
least one of said modulated signal and messages through said
communication interface.
32. The sensor of claim 29, further comprises a processor connected
to said accelerometer and said interface unit for controlling and
managing said accelerometer and said interface unit.
33. The sensor of claim 32, further comprises a memory means
connected to said processor for storing at least one of samplings
of said signal and instructions for operation of said
processor.
34. The sensor of claim 33, further comprising a positioning
circuit connected to said processor.
35. The sensor of claim 34, wherein said positioning circuit
comprises at least one of a gyroscope and a Global Positioning
System.
36. A sensing assembly comprising at least two sensors of claim
22.
37. The sensing assembly of claim 36, wherein said at least two
sensors are in communication with each other.
38. The sensing assembly of claim 37, further comprising a memory
means connected to said sensors for storing a unique identifier for
each one of said at least two sensors.
39. A sensor for detecting a displacement on a surface, said sensor
being In communication with a computer and comprising a semi
conductor substrate to which are integrated a semi conductor strain
gauge for outputting an electrical signal representative of said
displacement; an automatic gain amplifier for amplifying said
electrical signal; a control circuit for controlling a level of
amplification; a processor connected to said semi conductor strain
gauge for controlling and managing said semi conductor strain
gauge; and a positioning circuit connected to said processor.
40. The sensor of claim 39, wherein said electrical signal
comprises an analog electrical signal and wherein is further
Integrated to said semi conductor substrate an analog-to-digital
converter for converting said analog electrical signal to a digital
signal and wherein said control circuit controls a dynamic range of
said analog-to-digital converter.
41. The sensor of claim 19, wherein said mass is attached to the
substrate along a substantial portion of a circumference of said
mass.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of priority under 35 U.S.C
.sctn. 119 from Canadian Patent Application no. 2,366,030 filed on
Dec. 20, 2001, the disclosure of which is incorporated by reference
as if set forth in full in this document.
1. Field of the Invention
The present invention relates to the field of non-intrusive testing
of a medium located under a surface. More specifically, the present
invention is concerned with an intelligent profiling system
permitting the mechanical characterization of a medium under a
surface.
2. Background of the Invention
In the field of geophysical exploration for example, non-intrusive
techniques have been sought and developed as a supplement or an
alternative to conventional in-situ testing techniques involving
boring because these techniques are non-destructive. In some cases
where boring is not feasible, for example in granular soils, such
non-intrusive techniques are the only way to explore the
underground. Also, they generally are more cost-effective.
Non-intrusive techniques are also used for exploring a medium
situated under a surface in various other fields, for example, for
assessing the wear conditions of roads, of bridges, of bar joints
in buildings, of concrete walls, etc, or for detecting subsurface
pockets in mining or military applications.
Interestingly, surface waves, and especially Rayleigh waves, are
very useful in the field of non-intrusive testing. One of the well
known method in the art is Spectral Analysis of Surface Wave
("SASW"), for instance, which makes use of surface waves for
determining shear velocity profiles of the underground without
intrusion. This method involves a pair of sensors, at least one
source of impulses, and a signal processing system.
Although such a technique using surface waves permits exploration
of a broad range of thickness of soils, by changing the distance
between the two sensors and by using different sources of impulses,
in the case of SASW discussed hereinabove for instance, its
operation generally requires actions from a highly skilled worker
expert in the field in order to obtain useful information on the
subsurface medium under investigation.
Therefore, in spite of the efforts in the field, there is still a
need for a system allowing profiling of a medium under a surface,
comprising sensors, a generator of impulses and a user-computing
interface, and permitting collecting, analyzing, and processing the
data for display and use by a non-expert.
OBJECTS OF THE INVENTION
An object of the present invention is therefore to provide an
improved profiling system.
SUMMARY OF THE INVENTION
In one of its embodiments, the present invention relates to a
sensor for detecting an acceleration on a surface. The sensor
exchanging messages with a computing means through a communication
interface. The sensor comprises an accelerometer for outputting a
signal representative of the acceleration and an interface unit
comprising a transmitting circuit. The interface unit receives the
signal representative of the acceleration and modulates the same
for transmission to the computing means.
In another embodiment, the present invention relates to a sensor
for detecting an acceleration on a surface. The sensor exchanges
messages with a computing means through a communication interface.
The sensor comprises a substrate comprises an accelerometer for
outputting a signal representative of the acceleration. The sensor
further comprises a mass attached to the substrate. The mass moves
in response to the acceleration. The sensor also includes an
interface unit as described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
In the appended drawings:
FIG. 1 is a schematic representation of a profiling system
according to an embodiment of the present invention;
FIG. 2 is a perspective view of a displacement sensor used in the
profiling system of FIG. 1;
FIG. 3 is a top plan view of the displacement sensor of FIG. 2;
FIG. 4 is a sectional view taken along the line 4--4 of FIG. 3;
FIG. 5 is a top view of the substrate of the displacement sensor of
FIG. 2;
FIG. 6 is a diagram of a circuit equivalent to the displacement
sensor of FIG. 5;
FIG. 7 is a schematic sectional view of an energy impulsion
generator used in the profiling system of FIG. 1; and
FIG. 8 is a block diagram of a sensor in accordance with another
embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Generally stated, the system of the present invention enables a
non-intrusive physical analysis of mechanical characteristics of a
medium located under a surface, and a display of the results
thereof.
Such a medium separated from direct exploration by a surface can be
the underground, the thickness of a concrete wall, the thickness of
a joint bar and the like. For illustration purposes, the present
invention will be described using an embodiment dealing with
geophysical testing. Therefore, in the following, the medium to be
studied is a subsurface region of the underground, through the
surface thereof.
More precisely, the system of the present invention makes use of
sensors that detect the velocity of shear waves induced in the
subsurface region under test by means of an excitation generated by
a generator of impulses.
Turning now to FIG. 1 of the appended drawings, the system
according to an embodiment of the present invention will be
described.
Basically speaking, the system 10 comprises three units or system
components: a sensing assembly 12; an energy impulse generator 14,
(referred to in the following as EIG); and a user-computing
interface 16, (referred to in the following as UCI).
As can be seen in FIG. 1, the sensing assembly 12 comprises
displacement sensors 18 placed at various locations on a surface
20. The sensing assembly 12 may comprise a number of sensors 18
comprised between one sensor 18, which is located successively at
various locations, and a plurality of sensors 18. In a specific
embodiment of a system 10 according to the present invention, the
sensing assembly 12 comprises four sensors 18. Obviously, other
sensor quantities are possible as well. The role of the sensors 18
is to detect a movement in response to bursts of impacts generated
by the energy impulse generator 14 on the surface 20.
Each one of the displacement sensors 18 of the sensing assembly 12,
and the energy impulse generator 14, are connected to the
user-computing interface 16 by means of an communication interface
21. Many different techniques may be used to interconnect the
sensors 18 to the user-computing interface 16. For example, the
communication interface 21 may include fiber optics cables, coaxial
cables, multi-conductor cables, an optical link, a RF link, shown
in FIG. 1 under label 22. Alternatively, multiplexing means may be
considered for the interface of communication 21. Communication
interface 21 is used to relay messages, comprising instructions
and/or data, between system components.
As displayed in FIGS. 2 to 4, the sensor 18 is protected within a
housing. The housing may include a plate 27 and a casing 24 closed
by a top cover 25. Provided the surface 20 is not too hard, the
displacement sensor 18 is attached to the surface 20 by means of a
thread attachment 26 mounted on a plate 27 on which the casing 24
can be inserted and secured by edges 28 of the plate 27 (see FIG.
2a). Alternatively, in the case where the surface 20 is too hard,
the plate 27 can be fixed thereto by means of an adhesive 29 (see
FIG. 2b), or even simply deposited on the surface 20.
The casing 24 is provided with a communication connector 30 (see
FIG. 3) for connection to the user-computing interface 16 by means
of a connection 22 of the interface of communication 21 (see FIG.
1).
It is to be noted that the top cover 25 also supports a shock
absorbing element 32 and a damping element 34, which are
symmetrically located relative to a shock absorbing element 32' and
a damping element 34' attached to the casing 24, and may support an
optional communication antenna 36 or an optical diffuser (or
transceiver) (not shown).
A semiconductor substrate 42 is protected within the casing 24, as
shown in the cross section of FIG. 4. A mass 38 is supported within
an opening 40 of the semiconductor substrate 42 supporting strain
gauges 44 and resistors 46 and 48 (shown in FIG. 5). The mass 38 is
allowed to move in response to acceleration. As will easily be
understood by one skilled in the art, movement of the mass 38
induced by shear waves generated in the subsurface region under
surface 20 cause strains on the semiconductor substrate 42.
A person skilled in the art will understand that the semiconductor
substrate 42 and the elements which it supports (mass 38, strain
gauges 44, resistors 46, etc.) may be broadly referred to as an
accelerometer or an accelerometer assembly or unit. An
accelerometer may be broadly defined as a device whose response is
linearly proportional to the acceleration of the material (e.g., in
this case, a surface) with which it is in contact. A person skilled
in the art will understand that the accelerometer or sensor 18 need
not be in direct contact with the surface. Contact via other
intermediary elements or media is also considered.
As shown in FIG. 6, the circuit equivalent to the displacement
sensor 18 comprises four strain gauges 44 and two resistors 46
forming a Wheatstone bridge. One diagonal of the bridge is
connected to a DC voltage source 50, while the other diagonal of
the bridge serves as an output of the strain sensitive circuit and
is connected to an amplification unit 52. As will be explained
hereinbelow, the strain gauges 44 are used as transducers for
transforming a mechanical deformation on the semiconductor
substrate 42 into an electric signal (or other type of information
bearing signal). The resistor 48 is used for calibration purposes,
as will be described hereinbelow.
The strain gauges 44 are used to record the movement of the
subsurface region under test, transmitted to the displacement
sensor 18 by the mass 38. They are temperature-compensated by means
of the matched resistors 46. It is to be noted that the high
symmetry of the sensing circuit of FIG. 5 also contributes to the
temperature compensation by allowing balancing of the Wheatstone
bridge over a range of temperature.
The strain gauges 44 can be glued on top of the semiconductor
substrate 42, built up by deposit onto substrate 42, directly
etched thereto. The direct etching of the semiconductor substrate
42, by techniques known in the art, ensures a perfect location of
the strain gauges 44 together with a minimized temperature
mismatch, therefore a minimized stress concentration, thus enabling
the manufacture of a highly sensitive displacement sensor 18.
The displacement sensor 18 further comprises an interface board 53
(also referred to herein as an interface unit), shown in FIG. 4,
which supports the required communication circuitry attached to the
communication connector 30 and/or antenna 36. One of the
communication circuitry functions is to modulate the signal
representative of the surface acceleration (obtained from, for
example, the Wheatstone bridge). The modulation includes any
transformation of a signal to prepare for transmission over the
communication interface 21. As seen in FIG. 6, displacement sensor
18 may further include an analog to digital converter 47, a
transmitting circuit 49 (also referred to as sensor communication
means) and a control circuit 57. The control circuit 57 is used for
power management, to adjust the level of amplification of the
amplification unit 52 and its offset, during calibration to a
prefixed value. Frequency filtering means (not shown), compensation
and linearization means (not shown) may be added on substrate 42 to
alter the electrical signal from the Wheatstone bridge. In an
embodiment of the invention, substrate 42 also includes memory
means and processor (neither are shown in FIGS. 2 6). The control
circuit 57 also allows setting the dynamic range of the analog to
digital converter 47.
Of course, the type of circuitry depends in part on the type of
communication 22 of the interface of communication 21 between the
displacement sensors 18 and the user-computing interface 16.
The displacement sensor 18 can either be externally powered or
internally powered by means of an integrated power source 54 such
as batteries located underneath the semiconductor substrate 42 (see
FIG. 4). Such batteries can be located inside the casing wherever
convenient, or even in an extra casing outside the casing 24. In
another embodiment of the invention, sensor 18 may be powered
externally by radio-frequency signals.
As explained hereinabove in relation to FIGS. 2a and 2b, each
displacement sensor 18 may be simply deposited on the surface 20,
or secured thereto by means of an adhesive 29 (FIG. 2b), or
fastened thereto by means of a thread attachment 26 (FIG. 2a).
The damping element 34 attached to the top cover 25, and the
corresponding damping element 34' attached to the casing 24, may be
made of elastic or gel-like material. By ensuring a constant
absorption of energy over a range of temperature, and provided they
are made of a material having resistance to fatigue such as
neoprene or silicone for example, they optimize the damping factor
and contribute in maximizing the quality of the signal.
Indeed, the performance of the displacement sensor 18, as assessed
in terms of amplitude and phase distortion, depends primarily on
the magnification factor and the damping factor of the device.
The shock absorbing pads 32 and 32' are efficient in protecting the
displacement sensor 18 from excessive shock, for example during
handling.
Thermoplastic, elastic, sealing product or rubber joints 55 are
provided between the cover 25 and the casing 24 for sealing the
displacement sensor 18 and protection against adverse environment
(see FIG. 4).
It is to be pointed out that the fact that the displacement sensor
18 of the present invention comprises a semiconductor substrate 42
that has integrated strain gauges 44, amplification means 52 and
control circuitry 57, permits reducing the noise to signal ratio
and therefore the contamination of the signal during transmission
to the UIC 16. The possibility for the displacement sensor 18 to
include an analog to digital inverter 47 in case one such item is
needed also contributes to the reduction of the noise to signal
ratio during transmission.
Furthermore, people in the art will be aware that the use of
semiconductor strain gauges 44 enables achieving a gain superior to
that obtained by using conventional foil strain gauges.
It is also to be underlined that the use of a mass 38 contributes
to increase the responsiveness, and therefore, the measurement
capability, of the strain gauges assembly.
As is generally known in the art, the displacement sensor 18
according to the present disclosure operates as follows: when power
is fed to the circuit in absence of acceleration, the substrate 42
is not strained and the resistance of the strain gauges 44 is
maintained at its original level so that the output signal of the
circuit is zero. As an acceleration occurs, an external force is
applied on the mass 38, which causes deformation of the substrate
42 resulting in a change of the electric resistance values of the
resistance elements since the substrate 42 bends and deforms the
gauges 44. This deformation changes the nominal resistance of the
gauges 44, causing the equilibrium conditions of the Wheatstone
bridge to be broken, giving rise to a voltage output of the
circuit. One skilled in the art will understand that analysis of
this output voltage enables to obtain the characteristics of the
subsurface region under test.
Turning to FIG. 7 of the appended drawings, the energy impulse
generator 14 will now be described.
The energy impulse generator 14 comprises a spring 60 that is set
into compression by a motor assembly 62 so as to store energy and
to pull on an impact head assembly 64 through a latch 66. The
impact head assembly 64 is released by activating a solenoid 68
that pulls the latch 66, thus unlocking the impact head assembly
64, allowing the extension of the spring 60.
Obviously, the power source for the spring 60, here exemplified as
the motor assembly 62, could be a pneumatic, a hydraulic,
electrical or a mechanical source.
The spring 60 is used against the inertia of the impact head
assembly 64 and gives impulsion at the time of an impact, and also
as a means for holding back the impact head assembly 64 so as to
prevent it from bouncing back after an impact.
A strain gauge circuitry 63 (also referred to more broadly as a
strain measuring device), located on latch 66 for example or an
accelerometer 67 located impact head assembly 64, is used to
monitor the energy, which is stored into the spring 60, by
comparing it with the energy command transmitted by the UCI 16 to
the EIG 14 control circuit.
A damper 72 is provided to absorb the shock produced on the
assembly, while the energy impulse generator 14 thus transmits a
burst of energy by the impact of the impact head assembly 64 on an
element to be analyzed.
A control circuit (not shown) permits to monitor the amount of
energy release and the overall operation of the EIG 14. EIG 14 may
also include other circuitry (not shown) such as a processor which
operates and manages EIG 14; and memory means. Memory means
includes various types of memory such a s Random Access Memory
(RAM), Read-Only Memory (ROM), Electrically Erasable Programmable
ROM (EEPROM), etc. RAM is used during calculations, for data
storage, and for timestamp recording (from the processor 84 or a
sensor unit and to be transmitted or relayed). ROM comprises
initialization codes, start sequences, etc. EEPROM may comprise
operation algorithms, tables, sensor identification, etc. EEPROM
data may be received via communication interface 21.
A power pack 65 is provided for holding a battery. It also adds
weight to the overall structure of the EIG 14. Power pack 65 may
include rechargeable batteries. The batteries may be recharged in a
contact or contact-free (e.g., via RF) fashion. Power supply
through direct cable feed is also an option.
The EIG 14 is fastened to the surface 20 using threaded attachment
26 or other attachment means essentially similar to those used for
the displacement sensor 18 and described hereinabove. Other
examples of attachment means include a weight, magnetic material,
adhesive material, a "Ramset" or explosive driven type anchoring
means, etc. It is understood that these types of attachment means
can be used for sensor 18 as well.
The energy for activating the above described process of impact
generation is released by means of a command issued from the user
computing interface 16 (UCI) and transmitted to the EIG 14 through
a cable, an optical signal or a radio frequency signal. This
command triggers the loading and unloading of the mechanism and
thus the delivery of an energy pulse by the EIG 14.
The user-computing interface (UCI) 16, exemplified in FIG. 1,
comprises a number of subsystems: a user interface system,
comprising a keyboard, power and function keys, a display screen
and/or a touch screen and/or a voice recognition device; an
equipment interface, which allows connection to other output
devices such as printers (not shown); an interface system with the
IEG; a signal collecting system for collecting data from the
displacement sensors 18 of the sensing assembly 12; a processing
system, which performs the computations and manages the various
interfaces together; and a computer interface system that permits
connection to other computers.
Of course, the UCI 16 stores a program or algorithm that, for
example, can control the energy impulse generator 14 and the
displacement sensors 18, and collects and stores data from the
displacement sensors 18 of the sensing assembly 12. Furthermore,
this program may analyze the collected data to calculate some
properties or features of the medium under a surface and display
them.
It is to be noticed that each one of the different assemblies can
operate in an autonomous fashion, or powered by a central unit.
Most interestingly, provided the program and software stored in the
UCI 16 is adequate, the system of the present invention can be used
in a variety of applications.
For example, in the field of geotechnical testing, the system of
the present invention can be used to detect pockets or faults in
the underground, in the mining industry. As a further example, in
the military field, the system of the present invention can be used
in order to study the geological structure of a terrain for the
purpose of effective explosive positioning or hideouts uncovering.
The present system could be used to supply data to systems such as
the so-called JTIDS ("Joint Tactical Information Distribution
System").
Additionally, people, in the art will foresee the possibility of
adding GPS or gyroscope systems to locate each displacement sensor
18 of the sensing assembly 12, and the EIG 14. One possible
application is related to the identification of an underground
cavity and the determination of its spatial coordinates. An
algorithm can be introduced into the UCI 16 that maps, through the
use of a global positioning system (GPS), volumes that can be used
for underground concealed hideouts, facilities, etc. In military
applications in particular, such an algorithm may also be able to
detect any structural fault so as to allow planning accordingly
strategic delivery of payload in order to maximize the damage to
cavities or underground-concealed areas.
Another field of possible applications where the system 10 of the
present invention can be used, providing the adequate algorithm is
included into the UCI 16, is the communication field, taking
advantage of the property of low frequency shear waves to propagate
over long distances or great depths. Such a specific user-computing
interface 16 may perform unidirectional or bi-directional
communication, detect, identify and locate movements on the ground
surface. In this kind of application, the system 10 uses as a
transmitter an electromechanical device that induces energy at
various frequencies in the ground, resulting in ground waves. As
low frequency shear waves propagate deep into the ground and over
long distances, while high frequency waves can travel only short
distances, a communication signal consists of an energy signature
modulated in frequency and relative amplitude that initiates,
delivers, and ends a predetermined communication protocol. Due to
various reflections caused by the complex geophysical environment,
the transmitted signal is scrambled in time and frequency domain
durng its way therethrough. The sensing assembly 12, used at the
receiving end, in conjunction with the UCI 16, unscrambles this
signal so as to reconstruct the frequency domain and its variation
over time. The high frequency content thereof is used as a means to
securely position the source of the signal.
Additionally, the distribution of displacement sensors 18 enables
position triangulation of an emitter or of any signal sources
generated by troops, moving vehicles or impacts on the ground.
Reconstructing incoming signals, the UCI 16 may process pattern
recognition database to match signatures and identify an emitting
source.
A sensor 80 is shown in FIG. 8 in accordance with another
embodiment of the invention. Sensor 80 comprises an accelerometer
88 whose response is in relation to the acceleration of the surface
20 with which sensor 80 is in contact. Accelerometer 88 may
comprise strain gauges, capacitors, or piezo-electrical devices.
Accelerometer 88 can therefore be conventional type accelerometers,
but other technologies such as Micro Electro Mechanical Systems
(MEMS) or Nano Electrical Mechanical Systems (NEMS).
The signal (electrical or other equivalent message carrying type of
signal) representative of the acceleration produced by
accelerometer 88 is fed to amplifier 90. In an exemplary
embodiment, amplifier 90 is an automatic gain amplifier. Amplifier
90 may therefore act to increase the dynamic range of sensor 80.
The gain of amplifier 90 is transmitted to processor 84 which will
in turn the signal sent by RF communication circuit 102.
After amplifier 90, the signal is sent to a low-pass filter 92.
Low-pass filter 92 eliminates spectral aliasing in the frequency
domain and distortion in the time domain. Sample and hold device 94
then receives the signal, samples it and holds it for a period of
time sufficient for analog to digital converter 96 to perform its
conversion of the analog signal to a digital signal.
A person skilled in the art will understand that one can add a
second set of accelerometer (not shown), amplifier (not shown) and
low-pass filter (not shown) in parallel to the first set heretofore
described and feed sample and hold device 94. Sensor 80 described
above acts as a simple accelerometer. With a second accelerometer
placed so as to pick up acceleration in an axis which is
perpendicular to the axis of the accelerometer 88, sensor 80
becomes an inclinometer. In yet another embodiment of the
invention, sensor 80 may comprise a third set of accelerometer (not
shown), amplifier (not shown) and low-pass filter (not shown) in
parallel to the first and second sets heretofore described and feed
sample and hold device 94. With a third accelerometer placed so as
to pick up acceleration in an axis which is perpendicular to the
axis of both accelerometer 88 and the second accelerometer, sensor
80 becomes a gyroscope.
Persons skilled in the art will understand that one may calculate
speed from of the integral over time performed the signal
representative of the acceleration output by accelerometer 88. One
may also calculate distance by integrating speed over time. These
calculations may take place in processor 84.
Returning to the embodiment shown in FIG. 8, the signal from analog
to digital converter 96 is sent to low-pass filter 98 which will
remove undesired frequencies. Low-pass filter 98 may also be
incorporated within analog to digital converter 96. In order to
remove any distortions (in amplitude or phase) the signal is then
compensated and linearized in compensation and linearization device
100. The compensation and linearization device 100 will linearize
the signal in order to guarantee a uniform performance in regards
of the frequency component, and linearization device 100 will also
spread the frequency spectrum of the signal.
The signal is finally sent to communication circuit 102.
Communication circuit 102 send and receives messages comprising
instructions and/or data through a communication interface 21 to a
UCI 16 or to other sensors 80 (not shown) in a sensing assembly
similar to sensing assembly 12. Typical instructions include:
reset, initialization; download; new algorithms; linearization,
compensation and identification parameters (transmit or download);
calibration; transmission mode (e.g., direct, network); start of
sampling; energy conservation; etc. In network mode, a
communication protocol will establish the best path for
transferring data from sensor to sensor and finally to UCI 16.
Sensor 80 may therefore act as a data relay. Communication circuit
102 may be protected against electromagnetic interference. In an
embodiment of the invention, each sensor 80 has its own Internet
Protocol (IP) address and is addressed accordingly.
Sensor 80 also comprises a processor 84 which operates and performs
management of sensor 80. Sensor 80 comprises memory means 86.
Memory means 86 includes various types of memory such as Random
Access Memory (RAM), Read-Only Memory (ROM), Electrically Erasable
Programmable ROM (EEPROM), etc. RAM is used during calculations,
for data storage, and for timestamp recording (from processor 84 or
another sensor 80 and to be transmitted or relayed). ROM comprises
initialization codes, start sequences, etc. EEPROM may comprise
operation algorithms, tables, sensor identification, etc. EEPROM
data may be received via communication interface 21.
Power to sensor 80 is provided by power source 82. Power source 82
may include rechargeable batteries. The batteries may be recharged
in a contact or contact-free (e.g., via RF) fashion. Power supply
through direct cable feed is also an option.
Optionally, sensor 80 may also include a positioning circuit (not
shown) such as an electronic gyroscope or a Global Positioning
System (GPS) receiver.
In an embodiment of the invention, a housing 104 comprises three
sections. Housing 104 is hermetically sealed to protect all of its
components from external elements. A first section 106 holds the
batteries and power regulation circuitry. A second section 108
holds items 84 to 100 as well as the positioning circuit (not
shown). A third section 110 holds communication circuit 102.
Surface of section 110 is conductive thereby providing an
electromagnetic barrier to protect communication circuit 102 from
electromagnetic interference (EMI).
Although the present invention has been described hereinabove by
way of preferred embodiments thereof, it can be modified, without
departing from the spirit and nature of the subject invention as
defined in the appended claims.
* * * * *